Compounds of structure I are known and known to have HMG-CoA reductase inhibitory properties. They are the natural fermentation products mevinolin (U.S. Pat. No. 4,231,938) and compactin (U.S. Pat. No. 3,983,140) and derivatives thereof, all with the natural 2-methylbutyrate side chain.
Hydrogenation products, including tetrahydromevinolin are described in U.S. Pat. No. 4,351,844.
Some compounds of structure II with the 2,2dimethylbutyrate side chain and processes for their preparation are known in EPO published application 33538. However, the process disclosed therein involves 4 distinct chemical steps: (1) de-esterification of the 2-methylbutyrate; (2) protection of the 4-hydroxy of the pyranone ring; (3) re-esterification to form the desired 2,2-dimethylbutyrate; and (4) deprotection of the 4-hydroxy group.
Now, with the present invention there is provided a novel process for the preparation of compounds of structure II involving only one chemical step and resulting in overall yields much higher than those realized by the prior art process, with the expenditure of much less time, labor and materials.